Cupola for foundries and steelworks



Dec. 16, 1952 POUMAY 2,621,915

CUPOLA FOR FOUNDRIES AND STEELWORKS Filed June 30, 1949 -//A i in INVENTOR.

ADcl-PHE' M F POUMAY Patented Dec. 16, 1952 CUPOLA FOR FOUNDRIES AN 11) STEELWOBKS Adolphe Marie Francois Poumay, Jambes-Namur,

Belgium;

Adolphe-Maurice-Charles Poumay,

administrator of said Adolphe-Maric-Francois Poumay, deceased, assignor t Adolphe-Maurice-Charles Poumay, Wanze, Belgium Application June 30, 1949, Serial No. 102,322 In Belgium July 5, 1948 3 Claims.

My present invention relates to cupolas for foundries and steelworks in general and in particular to cupolas comprising one or more rows of twyers below the melting zone and further twyers blowing the air above the melting zone into the shaft of the cupola.

In existing cupolas, when there is only one row of twyers below the melting zone, these twyers are usually called melting twyers. When there are two superposed rows of twyers below the melting zone, the twyers situated in the lower plane are of larger section and admit the larger part of the total amount of air blow in, and for this reason they are called melting twyers or main twyers. With regard to those in the higher plane, they are of smaller section and admit a smaller quantity of air; for these various reasons they are called secondary twyers, auxiliary twyers or supplementary twyers.

All these various names, whether they relate to the main twyers or to the secondary twyers, conform completely to the functions of the respective twyers. Those of the lower row, that is to say, the main twyers, due to their wide section, admit the main part of the quantity of air to be blown in, which is required for the formation of the melting zone; those of the superposed row, that is to say, the secondary twyers, due to their smaller section, admit the additional air required to supplement the insufiicient quantity of air blown in through the main twyers or to burn the rising carbon monoxide.

It is well known that all the arrangements comprising a number of rows of twyers below the melting zone, designed and arranged as hereinbefore stated, have not in any case enabled the proposed objects to be achieved. The works of the metallurgical scientists of all countries have proved this. By way of example, the declaration by the German professor Dr. Ing. B. Osann in his Lehrbuch der Eisen und Stahlgiesserei, year 1922, page 93, will be literally quoted: There is no object in employing a sec- 0nd row of twyers. In order to obtain economical operation of the cupola, it is necessary that the temperature should decrease as rapidly as possible towards the top, in order that too much carbon monoxide may not be obtained in the gases escaping to the throat and in order to combat the reaction CO2+C=2CO. A second row of twyers runs counter to this. Moreover, these twyers are always clogged by slag. If it is desired to use them, they will be placed as near 'as possible to the lower row and they will be :given a blowingsection equal to one-half of that of the twyers of the lower row. It is also well known that these supplementary twyers have exer-ted other harmful influences; increase in height and lengthening of the'melting zone, correlative increase of the cold zone and of the oxidising zone, to the detriment of the quality of the metal decreasing in proportion with the drop in temperature undergone and with the increase in the oxidising reactions of its components; the qualitative output and the quantitative output of the cupolas have been reduced, without any increase in the output of heat.

It will readily be appreciated that it could not be otherwise, if reference is had to the experiments which were carried out with a cupola comprising a single row of twyers by Belden, under the auspices of the United States Bureau of Mines, Bulletin No. 54 Trans. Am. Foundrymans Asso, 22-1914, pages 1-40, and Stahl und Eisen, 34-1914, pages 360/4. These tests permitted the conclusion to be reached that there exists at the level of the twyers and above this level a zone of considerable cooling and of considerable oxidation, which is minimum at the centre and maximum at the periphery of the cupola. The rising gases necessitate a more or less long passage above the plane of the twyers in order that they may be substantially free from free oxygen. The lack of homogeneity in the gaseous mixture and the low temperature thereof permit the coexistence of carbon monoxide and of free oxygen without ignition.

The same conclusions regarding the existence of a zone of considerable cooling and of considerable oxidation above the plane of the twyers was reached by the German professor Dr. Ing. Walther Mathesius in his study published by Stahl und Eisen No. 30, year 1927.

Under these conditions, it will be understood that if a second row of secondary twyers is placed above the plane of the main twyers, the cold, oxidising zone of the cupola, will be extended due to the air fed to this second plane, and precisely at the point at which, due to a happy coincidence, the cupola had ceased to ,be cold and oxidising. The same harmful phenom ena as are produced by the main twyers of the lower row will be repeated and the intensification of the cold, oxidising zone is the only result afforded by the use of a second row of twyers. It will be understood why all the metallurgical scientists have advocated the exclusive use of a single row of twyers below the melting zone.

One of the objects of the present invention is not only to reduce, or to eliminate, the zone of cooling and oxidation generated by the twyers of the lower plane, but to permit the use of a secondary plane of twyers located above the first, the two planes being situated below the melting zone, without producing the harmful results hereinbefore referred to, but on the contrary with an improvement in the operation of the cupola, due to an increase in the thermal efficiency and a reduction in the rate of oxidation.

In contrast to the method hitherto universally followed, which consists in making the twyers of the higher plane smaller in section than the twyers of the lower plane, exactly the opposite procedure is adopted, that is to say, the twyers of the lower plane are of smaller section than the twyers of the higher plane, which are of larger section. When the cupola is in operation, the following will occur:

The twyers of the lower row, being of smaller section, will deliver the air in a quantity proportionate to the smallness of this section, that is to say, in an insufficient quantity to produce the creation of a zone of considerable cooling and of considerable oxidation like that generated by the existing cupolas, as has already been seen. The consequences will be: intense formation of carbon monoxide and very high temperature at the level of and above the plane of these twyers. Due to the insufficiency of the air blown in, the space which will have to be traversed by this air inside the cupola will be extremely small in order to lose all trace of free oxygen. All the oxygen blown in will be correspondingly more rapidly used up in the phenomena of combustion of the carbon of the coke and the combustion temperature will reach its maximum in minimum time. The rising gases, at the highest temperature, will be very rich in carbon monoxide and when they reach the plane of the main twyers they will combat, due to their high temperature, the cooling set up by these twyers. The temperature obtaining at the level of the main twyers will consequently be much higher than in all cupolas hitherto known. As a result, the rising CO coming from the small twyers of the lower plane will enter into a brisk combustion reaction with the free oxygen situated at the level of the main twyers, the existence of which oxygen in existing cupolas has been proved by Beldens experiments, which have been mentioned. There will be instant disappearance of the free oxygen and consequently complete disappearance of the oxidising zone. Moreover, the combustion of the rising CO will cause an enormous increase in temperature at the level of and above the main twyers and consequently the complete disappearance of the zone of considerable cooling which is present in existing cupolas. The melting zone will be brought to maximum temperature, greatly to the benefit of the temperature of the molten metal. Moreover, since the molten metal does not pass through any oxidising zone, it will not be subjected to the same oxidising infiuence as in all the methods adopted in the cupolas at present known.

As stated in the works of the German professor Dr. Ing. E. Piwowarsky, the best conditions will be obtained for the manufacture of castings of high strength. According to the opinion, hereinbefore stated, of Professor Dr. Ing. B. Osann, the intensification of the temperature in the melting zone will bring about a correlative intensification of the endothermic reaction CO2+C=2CO. This reaction will not result in any heat loss, provided that the cupola is provided, in accordance with the invention, with regenerating twyers which blow the air into the charging column above the reduction zone and will burn up the CO generated. All the latent heat of the rising gases will thus be recovered and the heat gained by the reaction CO+O=CO2 will serve to preheat the charges in their descent towards the melting zone. With regard to the pyrometric effect obtained in the melting zone, it has been seen that it will have been brought to a maximum. The output from the cupola will be optimum from the thermal, pyrometric, quali tative and economic viewpoints.

The technique adapted with modern cupolas has established the preference for using twyers set back in the masonry by narrowing the diameter of the profile above the twyers. This arrangement has the result (1) of reducing the surface of the oxidising zone at the level of the twyers, and (2) freeing the twyer orifices opening into the cupola, the slag thus being unable to reach the said orifices.

Hitherto, this arrangement has only been employed in cupolas comprising a single row of twyers below the melting zone. Due to the eascade arrangement of the profile of the refractory in the case of the invention, it is possible to use the aforesaid arrangement in cupolas comprising a plurality of rows of twyers below the melting zone. This arrangement constitutes the second main part of the invention. The advantages previously mentioned are obtained. in each row of twyers.

To sum up, the advantages aiforded by the invention are the following:

1. Elimination of the cold zone and of the oxidising zone by employing below the melting zone, twyers of reduced section located in the lower row, which twyers will be called CO twyers and supply the carbon monoxide which is to serve, by its combustion with the free oxygen (CO+O=CO2) in the upper row of main twyers of large section, below the melting zone, which will be termed CO2 twyers, for the elimination of the said free oxygen.

These twyers are disposed either quincuncially, or on a common vertical generatrice, in relation to one another.

This entirely novel arrangement produces exactly the opposite to what has hitherto always been done with all cupolas comprising two or more rows of twyers below the melting zone, which has always consisted in placing the main twyers of large section in the lower plane, while the twyers of the superposed plane or planes have always been of smaller section than the twyers of the lower plane.

2. Reduction of the oxidising zone and freedom of the twyer orifices opening into the cupola, due to the use of the profile in cascade of the refractory lining, this entirely novel arrangement being carried into effect by the immediate reduction of the diameter of the profile of the refractory lining above each row of twyers below the melting zone in the case of each one. The additional advantages obtained by these entirely novel arrangement are in particular:

(1) Closer location of the region of the twyers to the melting zone, that is to say, reduction of the distance between the melting zone and the region of the twyers.

(2) Reduction of the height of the melting zone, which will be as narrow as possible, and consequently very considerable increase in the temperature of the melting zone with the greatest possible benefit to the increase of the temperature of the molten metal.

(3) Increase in the temperature of the whole chamber, from the plane of the lower CO twyers to the reduction zone (CO2+C=2CO) above the melting zone.

(4) Greater freedom of the twyer orifices opening into the cupola and consequently greater regularity in the whole operation; less work to be done by the fan owing to the lower resistance to the fiow of the air set up by the twyers.

(5) Reduction in the loss by oxidation owing to the reduction of the oxidising zone.

(6) Saving of fuel owing to the increase produced in the temperature.

('7) Higher temperature of the molten metal and of the slag and consequently better desulphurisation of the metal, better purification of the metal by re-adier liquation of the dissolved oxides and metallic and other inclusions.

(8) Increase of the specific rate of melting per hour.

(9') Less recarburisation, due to the saving of fuel, will facilitate the working up of metal of low total carbon content, that is to say, of highstrength metals.

(10) Improvement of the thermal, pyrometric, metallurgical and economic efiiciency of the cupola.

The accompanying drawings show by way of non-limitative example an embodiment of the invention in its application to a cupola for use in foundries and steel-works.

Figure 1 is a view in vertical section on the line l-l of Figs. 2 and 3, and Figures 2 and 3 are horizontal half-sections on the lines 2-4 and 3-3 of Figure 1.

The cupola is composed of a cylindrical body I consisting of riveted metal plate, and comprising a refractory lining 3 insulating material 2 disposed between I and 3. A wind box 4 comprising inspection windows 5 supplies the air to a l the twyers 6, l and 8. The carbon monoxideforming twyers 6 in the lower plane are of small calculated rectangular section, resting on the longer side of the rectangle, the height of the latter being as small as is practically possible in order to effect the blowing in sheet form for the purpose of obtaining the thinnest possible melting zone in association with the large twyers l, but principally in order that the wind may immediately come into contact with the largest possible volume of fuel for a rapid utilisation of the oxygen blown in and an intensified formation of CO correlatively to the smallness of the quantity of air blown in. The absence of excess air and of free oxygen eliminates the cold zone and oxidising zone. The profile in cascade form of the refractory lining, as indicated in Figure l by the reference I l, permits the reduction of the oxidising zone in proportion with the size of the set-back peripheral annulus generated by the narrowing of the diameter immediately above the plane of the twyers. The molten metal in the form of droplets coming from a region of smaller diameter does not pass through this set-back peripheral annulus during its descent and, in proportion with the size of the surface of this an nulus, escapes the cooling and oxidising influence of the air blown in through the small twyers 6. The same will be the case with the slag; the molten metal and the slag cannot soil and obstruct the mouth of the twyers 6, which will remain perfectly free. The wind will penetrate without impedance and the rate of combustion will remain uniform. The work to be done by the fan will be less and the gain in driving force will be proportional to the greater freedom obtained in the twyers. The twyers 1 of wide section are the melting twyers proper or the main or CO2- forming twyers, and they have the same form and the same descending arrangement as the small CO twyers in the lower plane. Like the latter twyers, they are also set back in the refractory due to the immediate narrowing of the diameter of the profile above their plane; they are of much larger dimensions, that is to say of much larger section, than the twyers in the lower plane. With regard to the molten metal and the slag, the phenomena hereinbefore described with reference to the twyers 6 occur at the level of these twyers l.

The distance between the two planes of the twyers 6 and I must be sufiicient to ensure the arrival at the plane of the main twyers 1, of rising gases rich in carbon monoxide. As is known, the gases have a tendency to flow along the walls of the cupola, where there is less resistance to flow. In their upward movement, they therefore partly encounter the peripheral projection comprised in the refractory profile in the up er plane of the main twyers due to the narrowing of the inner diameter, the repelling effect exerted on the rising gases by the peripheral projection of the refractory, combined with the diametral direction of the radial air jets issuing from the twyers I, in co-operation with the expansion effect produced by the heat and the torsional effect due to the rectifying action exerted by the draft of the cupola, which acts as a shaft, sets up an intense whirling of the gases and of the air, which become intimately mixed and give rise to a brisk combustion of the rising CO (CO+O=CO2). This reaction shows that the free oxygen will disappear at the level of the twyers 1. The temperature will be brought to the maximum and the same will be the case with the molten metal and the slag flowing through this excessively hot non-oxidising zone. With regard to the regenerating twyers 8 disposed in the form of helices or otherwise between the melting zone and the throat of the cupola, they have the object of burning the CO- emanating from the reduction zone (CO2+C=2CO) following CO+O=CO2 and of thus recovering the latent heat of the rising gases, whereby any heat loss is avoided. The heat recovered serves to preheat the descending charges. These twyers are provided with a delivery cock 9 and a pressure intake cock ID for controlling the supply of air to tuyres 8. The features of these twyers, i. e. dimensions, number, arrangement, and delivery and pressure of the wind, are obviously functions of the rate of melting per hour of the cupola and of the physical necessity to avoid the creation of any supplementary melting zone or any melting point in the charging column.

What I claim is:

1. In a cupola furnace, a single air-supply chamber surrounding the furnace in the region just above the hearth thereof, a first set of lower tuyeres communicating with said air-supply chamber, a second set of tuyres disposed on a level above said lower tuyeres and communicating lso with said air-supply chamber, all those tuyeres being arranged so as to blow air for the combustion in the part of the cupola containing only the bedcoke in ignition, each of said lower main tuyeres having a cross-sectional area smaller than the cross-sectional area of said upper tuyeres all the tuyeres of both sets blowing air provided by the air-supply chamber at the same pressure but in different quantities according to the cross area of the tuyres of both sets the said cross areas and the distance between the two planes of said sets of tuyeres being such that the air blown by the lower set of tuyeres causes the generation of a large amount of carbon monoxide gas whilst the plentiful supply of oxygen contained in the air admitted through said upper set of tuyeres reacts with the carbon monoxide gas produced from the air which entered said first set of tuyeres to form carbon dioxide whereby to reduce the zone of cooling and oxidation above the level of lower tuyeres, the wall portion at which the lower tuyeres are located and the wall portion directly thereabove where the upper tuyeres are opening being both parallel to the longitudinal axis of the cupola and being connected by an annular surface which is perpendicular to the longitudinal axis of the cupola and an annular surface perpendicular to the longitudinal axis of the cupola being also provided above the upper set of tuyres whereby all the tuyeres of both sets are set back by a reduction of the interior diameter of the wall portion substantially at the plane formed by the upper parts of the tuyeres of each set.

2, A cupola furnace, comprising in combination, a metal bath zone located at the bottom of the furnace; a melting zone located above and spaced from said metal bath zone; an air-supply chamber surrounding said furnace; a first set of tuyres communicating with said air-supply chamber and being located below said melting zone and at a distance above said metal bath zone sufiicient to prevent air from said first set of tuyeres from contacting any molten metal, said first set of tuyeres being located in a part of said cupola furnace which has a first inner wall portion which extends in a direction parallel to the longitudinal axis of the cupola and is set back from a second inner wall portion of the cupola which is directly above said first wall portion, said first and second wall portions being joined by an annular wall portion of said cupola furnace which is located in a plane substantially perpendicular to the longitudinal axis of said cupola; and a second set of tuyres communicating with said air-supply chamber and being located above said first set of tuyeres, said second set of tuyeres having a total cross-sectional area which is substantially larger than the total crosssectional area of said first set of tuyeres, and

said second set of tuyeres being located in said second inner wall portion of said cupola, said second inner wall portion of said cupola being set back from a third inner Wall portion of said cupola which is directly above said second set of tuyres, said second and third inner wall portions being joined by an annular wall portion of said cupola furnace which is located in the plane substantially perpendicular to the longitudinal axis of said cupola.

3. A cupola furnace, comprising in combination, a metal bath zone located at the bottom of the furnace; a melting zone located above and spaced from said metal bath zone; an air-supply chamber surrounding said furnace; a first set of tuyeres communicating with said air-supply chamber and being located below said melting zone and at a distance above said metal bath zone sufficient to prevent air from said first set of tuyeres from contacting any molten metal, said first set of tuyeres being located in a part of said cupola furnace which has a first inner wall portion which extends in a direction parallel to the longitudinal axis of the cupola and is set back from a second inner wall portion of the cupola which is directly above said first wall portion, said first and second wall portions being joined by an annular wall portion of said cupola furnace which is located in a plane substantially perpendicular to the longitudinal axis of said cupola; a second set of tuyeres communicating with said air-supply chamber and being located above said first set of tuyres, said second set of tuyeres having a total cross-sectional area which is substantially larger than the total cross-sectional area of said first set of tuyres, and said second set of tuyeres being located in said second inner wall portion of said cupola, said second inner wall portion of said cupola being set back from a third inner wall portion of said cupola which is directly above said second set of tuyeres, said second and third inner wall portions being joined by an nnular wall portion of said cupola furnace which is located in the plane substantially perpendicular to the longitudinal axis of said cupola; and a third set of tuyeres communicating with said air-supply chamber and being located above said second set of tuyeres.

ADOLPHE MARIE FRANQOIS POUMAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 290,343 Morgan et a1. Dec. 18, 1883 316,669 Smith et a1. Apr. 28, 1885 445,056 Greiner Jan. 20, 1891 986,792 Zipplel' Mar. 14, 1911 1,133,317 Rice Mar. 30, 1915 1,640,251 Poumay Aug. 23, 1927 FOREIGN PATENTS Number Country Date 5,890 Great Britain Mar. 17, 1900 (A. D. 1899) 478,819 Great Britain Jan. 26, 1938 

